Ultrasound and ultrasonic imaging has made great advances in recent years do to improved transducers, computer analysis of the return signal and the incorporation of Doppler analysis of the image. US equipment is standard equipment in all hospitals and many clinics. The use of ultrasound is critical for locating catheters in veins during endovascular procedures. In most cases the resolution and gain of current equipment is sufficient to see the catheter and interpret the image, although it is common to use a specially trained technician to operate the device because it does require training and skill that few doctors have. The Doppler mode on these ultrasound machines is typically used to show movement of blood in veins or arteries. The Doppler frequency shift of sound that reflects of moving objects is displayed with a color on the ultrasound image that shows tissue or blood movement. The intensity and duration of this movement can be used to diagnose reflux in leg veins that are caused by incompetent valves and result in varicose veins.
Doppler is also used to image blood flowing in the heart to show efficiency and functionality of heart valves. When the target structure is very deep in tissue as when imaging veins in the thigh, it can be very hard to resolve the structure. In fact, imaging the end of the catheter is considered to be one of the most difficult parts of an endovenous procedure such as varicose vein treatment. In many cases, if the catheter is not imaged properly it is possible to treat the wrong section of the vein or even the wrong vein causing severe complications or even death. There is a great need to improve the ability to see inside the body. It would be advantageous to enhance the visibility of the location of catheters.
In addition there is a need to drain blood and reduce the diameter of vessels during endovenous ablation for the treatment of varicose veins. This can be accomplished by elevating the leg, applying compression, or injecting vasoconstrictors near the vein. It is also possible to cause the vein to shrink in size and force out blood by stimulating the vein to react in a way that is called a “spasm”. This is a natural body reaction to insult or injury that helps protect the venous system. During some types of surgery, particularly endovenous ablation, it helps to try to force the vein to spasm after the catheter is inserted so blood is forced out of the vein that may interfere with the ablation process. The prior art fails to teach a device that is able to vibrate inside the vein at about 500 Hz and tickling the entire internal length of the vein.
Pain management is a big part of the practice of many doctors, especially since more procedures are being done under local anesthesia in the doctor's office instead of in the hospital under general anesthesia. With the patient awake, the practice of certain procedures requires different techniques to prevent the patient from perceiving pain. It has been known that it is possible to distract patients from pain sensations and to stimulate nerves with a secondary sensation that blocks the transmission of a pain. Dentists commonly do this by pinching the cheek prior to injecting anesthesia and the vibrations from a motorized liposuction probe can mask the sensations of a needle penetrating the skin. The prior art fails to teach a way to do this inside the body in previously inaccessible locations by transmitting the distracting vibrations down a catheter or probe to the internal treatment site.
Prior devices to enhance imaging of internal structures using sound energy have concentrated on a couple of techniques:
1. Increasing the acoustic reflectivity of devices inserted into the body.
2. Placing ultrasound transducers on the device inside the body and detecting the emissions externally.
3. Transmitting longitudinal US waves down waveguides into the body and detecting the return waves along the same waveguide.
One major disadvantage of prior art imaging systems is the very low signal to noise ration of the technology. When the device to be imaged has an acoustic reflectivity that is close to that of the surrounding tissue it is very hard to get enough sound to bounce off of it to be imaged. This is especially true for small objects like a fiber optic catheter.
The acoustic density of glass or metal is close enough to that of blood or tissue that a piece of glass is very hard to image. In many cases introducing air into the tip of the catheter is not feasible. Air to tissue has a very large difference in acoustic density so that an air tissue interface reflects sound very well. Many prior art devices use air to enhance imaging.